Messages in this thread | | | Date | Tue, 21 Nov 2023 22:09:55 +0000 | From | Qais Yousef <> | Subject | Re: [PATCH v3 1/2] sched/schedutil: Rework performance estimation |
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On 11/23/23 08:47, Vincent Guittot wrote:
> > > > And is it right to mix irq and uclamp_min with bw_min which is for DL? We might > > > > > > cpu_bw_dl() is not the actual utilization by DL task but the computed > > > bandwidth which can be seen as min performance level > > > > Yep. That's why I am not in favour of a dvfs headroom for DL. > > > > But what I meant here is that in effective_cpu_util(), where we populate min > > and max we have > > > > if (min) { > > /* > > * The minimum utilization returns the highest level between: > > * - the computed DL bandwidth needed with the irq pressure which > > * steals time to the deadline task. > > * - The minimum performance requirement for CFS and/or RT. > > */ > > *min = max(irq + cpu_bw_dl(rq), uclamp_rq_get(rq, UCLAMP_MIN)); > > > > So if there was an RT/CFS task requesting a UCLAMP_MIN of 1024 for example, > > bw_min will end up being too high, no? > > But at the end, we want at least uclamp_min for cfs or rt just like we > want at least DL bandwidth for DL tasks
The issue I see is that we do
static void sugov_get_util() { .. util = effective_cpu_util(.., &min, ..); // min = max(irq + cpu_bw_dl(), rq_uclamp_min) .. sg_cpu->bw_min = min; // bw_min can pick the rq_uclamp_min. Shouldn't it be irq + cpu_bw_dl() only? .. }
If yes, why the comparison in ignore_dl_rate_limit() is still correct then?
if (cpu_bw_dl(cpu_rq(sg_cpu->cpu)) > sg_cpu->bw_min)
And does cpufreq_driver_adjust_perf() still need the sg_cpu->bw_min arg actually? sg_cpu->util already calculated based on sugov_effective_cpu_perf() which takes all constraints (including bw_min) into account.
Thanks!
-- Qais Yousef
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